Assembly and core transformation properties of two tetrahedral clusters: [FeIII13P8W60O227(OH)15(H2O)2]30− and [FeIII13P8W60O224(OH)12(PO4)4]33−

Abstract

Two nanosized 2.6 nm Fe^III substituted polyoxotungstates [Fe^III₁₃P₈W₆₀O₂₂₇(OH)₁₅(H₂O)₂]³⁰⁻ (1) and [Fe^III₁₃P₈W₆₀O₂₂₄(OH)₁₂(PO₄)₄]³³⁻ (2) are presented herein. Both clusters are synthesized from the reactions of trilacunary polyoxotungstate precursor [α-P₂W₁₅O₅₆]¹²⁻ and FeCl₃ under strict pH control at atmospheric pressure. The compounds are fully characterised in the solid state (FTIR and single-crystal XRD, elemental and thermogravimetric analyses), solution (cyclic voltammetry and UV-Vis spectroscopy) and in the gas phase (ESI-MS). An {Fe^III₁₃} core is present in both clusters which can be described as Archimedean solids (truncated tetrahedron, 1; elongated cuboctahedron, 2). 1 shows iron delivery properties coupled to a K⁺-triggered transformation of the {Fe₁₃} core to a {K⊂Fe₁₂} core in solution. Cyclic voltammetry shows the presence of independent W- and Fe-centred redox processes that support the stability of the clusters in solution. ESI-MS analyses confirm further the stability of 1 and 2 in the gas phase.